The present invention rleates to phonograph turntables and in particular to automatic controls for such turntables.
In automatic turntables, means are provided to lift the phonograph tone arm from a record after the tone arm cartridge has tracked all the information bearing grooves of a record. The mechanism for such tone arms has generally consisted of a segmented gear which travels with the tone arm. As the tone arm approaches the center of rotation the record supporting platter, the segmented gear meshes with another gear to set in motion the lifting of the tone arm from the record surface and shut down of the turntable.
It is important that the tone arm cartridge be lifted from the record as soon as possible after it has completed tracking the record grooves since the center of the record discs almost always contains a label which can do damage to the cartridge stylus. In addition, when the tone arm reaches the center of the record and is no longer tracking an information groove, it very often skates across the center portion of the record and may bang against the turntable spindle thereby posing the possibility of damage being done to the tone arm and/or cartridge.
The principal shortcoming of mechanisms heretofore available for lifting the tone arm from the record at the completion of play is that by their design a certain amount of skating across the record label must occur before the lifting mechanism is actuated. This is due at least partly to the fact that the mechanism must operate regardless of the record size.
Another shortcoming of such prior art devices is that the tone arm must carry with it at least a portion of the actuating mechanism thereby effecting the response of the system.
In view of the above, it is the principal object of the present invention to provide an improved mechanism for use with a phonograph turntable for automatically lifting the turntable tone arm from a record after the tone arm has traversed a preselected distance along the record grooves.
A further object is to provide such a mechanism which may be varied as desired to have the lifting operation initiated when the tone arm reaches any preselected position.
A still further object is to provide a mechanism which is relatively simple and inexpensive to construct and which may be easily adapted for use in conventional turntables without requiring any major redesign of the turntable.